Combine butter and sour cream in a large mixing bowl and whisk until well blended. Add granulated sugar, vanilla extract, and butter extract. Beat at medium speed for 3 minutes or until well blended. Add eggs one at a time, beating after each. Continue to mix batter for 2 minutes or until well blended.
In a separate bowl, sift together 2 cups flour, baking soda, and salt. Add flour mixture and buttermilk alternately to butter-sugar mixture, beginning and ending with flour mixture; beat after each addition. (The sifting and alternating may seem fussy, but it will guarantee the lightest possible cake).
Prepare baking pans: coat bottom of two round 9-in. baking pans with cooking spray; line bottoms with wax or parchment paper (trace around the bottom of your pan to cut out the correct paper size/shape). Coat wax paper with cooking spray. Place 1 T. flour in pan. Tap and rotate the pan to coat all interior surfaces, then tap out any extra flour into the sink or trash.
Divide batter evenly into prepared pans. Bake for 20-23 minutes or until a wooden pick inserted in center comes out clean. Cool in pan 10 minutes on a wire rack; remove from pan. Carefully peel off wax paper and follow How to Create the Most Moist Cake You’ve Ever Bakedor set aside to cool completely.